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VII. Alluvial Valley Floors - Rules 2.06.8 and 4,24 Alluvial Valley Floor Identification Information pertinent to alluvial valley floor (AVF) determinations is provided on pages 2.06-1 through 2.06-17j-4, Map No. 5 (Surface Geology), Map No. 15 (Alluvial Valley Floors, Land Use and Water Rights), and the supplemental report of September 22, 1986, "Material Damage Standard for Irrigation". Map No. 6 (Twentymile Park Hydrology) from Colorado Yampa Coal Company (CYCC) Permit C-81-071 is incorporated by reference. Potentially affected portions of Foidel Creek, Middle Creek, Fish Creek and Lower Trout Creek stream valleys have previously been evaluated with respect to AVF criteria in a number of coal permits, including Twentymile Coal Company's Foidel Creek Mine (C-82-056) and Fish Creek Tipple (C-81-036) and Colorado Yampa Coal Company's Eckman Park, Mine No. 1, and Mine No. 2 (C-81-071) and Mine No. 3 (C-84-062). To summarize the previous AVF findings made by the Division; Fish Creek alluvial deposits within and below the proposed permit area, an alluvial body in Sections 21, 22 and 28 (T5N, R86W) on Foidel Creek below the proposed permit area, alluvial deposits in the vicinity of the Foidel Creek/Middle Creek confluence downstream to Trout Creek, and alluvial deposits on Trout Creek downstream to the Yampa River were determined to be alluvial valley floors. Fish Creek was determined to be an AVF based on existing and potential flood irrigation and subirrigation capabilities and findings were made that farming would not be interrupted, discontinued or precluded; proposed operations would not cause material damage to quantity and quality of surface and ground water that supply the AVF, and the proposed operation would be conducted to preserve the essential hydrologic functions of the AVF. An alluvial body on Foidel Creek downstream from the permit area below the water gap in Sections 21, 22 and 28 (T5N, R86W) was determined to be an AVF based on an assumed capability to support subirrigation. As in the case of Fish Creek, findings were made to the effect that the AVF would not be negatively impacted by the proposed mining operation. An alluvial body upstream from the water gap in section 28, 29, 31 and 32 (T5N, R86W) was determined not to be an AVF based on a finding of insufficient water to support flood irrigation and a determination that subirrigated areas were less than 10 acres in extent and supported species which were not agriculturally useful. Alluvial deposits in the vicinity of the Foidel Creek/Middle Creek confluence and alluvial deposits on lower Middle Creek and Lower Trout Creek (below Middle Creek confluence) were found to be alluvial valley floors because of a presumed capability to support flood irrigation and subirrigated crops. Again, findings were made that the alluvial valley floors would not be negatively impacted by the proposed mining operation. -18-